Furnace electrode clamp

ABSTRACT

This invention relates to an electrode clamp embodying two graphite pads or liners which are each key slotted into the clamp body in dovetail-like fashion. The front surfaces are partcylindrical to mate with the surface of the electrode while the rear surfaces are plain. A water coolant conduit is provided in the clamp body extending alongside the pads providing &#39;&#39;go&#39;&#39; and &#39;&#39;return&#39;&#39; paths.

United States Patent [1 1 Winter et al.

[4 1 Apr. 16, 1974 FURNACE ELECTRODE CLAMP [75] Inventors: Frank Donald Winter; Laurence Derrick Truswell, both of Sheffield,

England [73] Assignee: British Steel Corporation, London,

England [22] Filed: July 9, 1973 211 Appl. No.: 377,306

[30] Foreign Application Priority Data July 7, 1972 Great Britain 32015/72 [52] US. Cl. 13/16 [51] Int. Cl. H05b 7/10 [58] Field of Search 13/14, 15, 16,17

[56] References Cited UNITED STATES PATENTS 3,457,355 7/1969 Guerrieri 13/14 3,509,261 4/1970 Phillips 13/16 X Primary Examiner-Roy N. Envall, Jr. Attorney, Agent, or Firm-Bacon & Thomas [5 7] ABSTRACT This invention relates to an electrode clamp embodying two graphite pads or liners which are each key slotted into the clamp body in dovetail-like fashion.

The front surfaces are part-cylindrical to mate with the surface of the electrode while the rear surfaces are plain. A water coolant conduit is provided in the clamp body extending alongside the pads providing go and return paths.

8 Claims, 3 Drawing Figures FURNACE ELECTRODE CLAMP This invention relates to furnace electrode clamps and more specifically relates to clamps for carbon electrodes employed in electric arc furnaces, particularly coated electrodes.

In electric arc furnaces power is supplied to the charge through carbon electrodes which are connected through clamps to bus bars carrying the transformer output current. Normally, the clamp comprises a copper body portion having a part-cylindrical surface corresponding to and mating with that of the electrode, the latter being drawn into firm contact with this surface through a band or yoke which embraces the electrode. Whilst this is satisfactory for plain carbon electrodes it is not suitable for such electrodes which have a current conducting protective coating on them, since frequently the metals of the coating and the body together form a eutectic system causing local melting at the operating temperature. This manifests itself as welding and pitting of, the contact surfaces which, in turn, increases the electrical contact resistance aggravating the situation whereby local arcing begins to develop causing further deterioration.

This particular problem may be overcome or mitigated by providing for the contact with the electrode to be made via an arcuate section graphite liner secured to the copper body. This solution however is not without drawbacks because the graphite is susceptible to oxidation which again adversely affects contact resistance, and such liners are expensive, they are liable to fracture by reason of their shape which, in addition, makes them difficult to machine and they are difficult to manoeuvre and assemble which gives rise to extended down-time periods when they are replaced.

It is an object of this invention to provide an improved furnace electrode clamp.

From one aspect the present invention provides a furnace electrode clamp comprising a metallic body portion and at least one graphite pad mounted on the surface of the body portion against which the electrode is clamped, the pad being located in and retained by a key slot in the body.

The slot is preferably machined to define a dovetaillike section axially of the electrode, whereby the pad may normally be inserted in and removed from the slot in a vertical direction, a stop member being provided along the bottom of the slot against which the pad abuts. The inner wall of the slot is preferably planar, matching the rear face of the pad, the front face of which being part-cylindrical to match the surface of the electrode.

Preferably a plate is bolted on to the body portion extending over the top end of the slot and overlapping the top of the pad so as to secure it firmly. A water coolant conduit may be provided within the body portion running alongside the pad.

More than one such pad and associated key slot, etc. may of course be provided in the body portion, and two are particularly advantageous since it provides three point contact with the band although the band may itself provide dual contact areas. The provision of two pads/key slots also facilitates the coolant design since the go and return paths may separately run alongside these two.

The two graphite pads or liners are individually more manageable than a single pad of more thantwice the size and weight, and their basic cost is less expensive as also is the machining and fabrication involved, in comparison with the single arcuate section pad employed hitherto.

In order that the invention may be fully understood, one embodiment thereof will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a plan view of a furnace clamp according to the invention with an electrode in situ;

FIG. 2 is a side elevation of the FIG. ll arrangement; and

FIG. 3 is a part-section along IIIIII in FIG. 1.

Referring now to FIGS. 1 and 2 in the drawings, the clamp comprises a body portion 1 made from copper having an upper tang 2 for bus-bar connections from the power supply and a lower portion 3 having an inwardly facing generally part-cylindrical surface 4. Two bosses 5 protrude from opposite sides of the body and provide bearings for a stirrup member 6 which is movable about the axis of the bosses in the direction of the arrow by hydraulic/pneumatic means (not shown). The lower end 7 of the stirrup extends through slots 8 formed in an austenitic stainless steel band 9 which embraces a coated electrode 10 extending through the clamp, the band being designed to have two inwardly protruding surfaces 11 for firmly contacting the electrode.

The copper body portion is additionally provided with a U shaped conduit 12 for water (coolant) and two dove-tail like slots or recesses 13 are machined into the cylindrical surface 4 alongside the path of this conduit.

Mounted within these slots are two high-strength graphite pads 14 which have a part cylindrical front surface corresponding to that of the electrode and a plain back, these pads being inserted into the slots from above and seating on a strip of insulating material 15 (e.g. Sindanyo) along the base of the body (FIG. 3). These pads are secured against withdrawal by two austenitic stainless steel plates 16 which are mounted on the upper surface of the body by stainless steel studs/- nuts and overlap the pads.

In operation the electrode 10 is inserted through the aperture defined by the band and the copper body with the stirrup moved into a forward position so as to allow freedom for this movement. Subsequently, with the electrode in place the stirrup is moved back drawing the band with it and firmly clamping the electrode against the graphite pads secured in the body portion, the graphite contact providing a very low contact resistance as compared with the band/electrode contact.

Withdrawal of the electrode is effected in the reverse fashion and replacement of the graphite pads can readily be effected merely by detaching the plates 16 and physically removing the pads from the key slots provided.

Although this invention has been described with reference to the particular embodiment illustrated, it is to be understood that various modifications may readily be made without departing from the scope of this invention. For example, more than two pads may be employed for effecting contact or even a single centrally disposed one could be utilised instead of the two shown. Further, it is not essential for the slots to be formed in the dovetail fashion and any other keyed shape could be adopted consistent with facilitating the machining and fabrication of the graphite pads.

We claim:

1. A clamp for a non-consumable coated electrode in an electric arc furnace comprising:

a metallic body portion defining a key slot on one surface thereon;

a U shaped band mounted for movement on the body and adopted to embrace the electrode; and

a graphite pad mounted in and retained by said slot against which the electrode is arranged to be clamped by said movable band.

2. A clamp according to claim 1, in which the key slot is a machined dovetail-like section extending axially of the electrode whereby the pad may be inserted in, and removed from, the slot in a vertical sense and in which a stop member is provided along the bottom of the slot against which the pad abuts.

3. A clamp according to claim 2, in which the slot has a planar inner wall, matching the rear face of the pad, the front face of the pad being part-cylindrical to match the surface of the electrode.

4. A clamp according to claim 3, in which the body defines a water-coolant conduit running alongside the pad.

5. A clamp according to claim 4, comprising,

at least two of said pads and a like number of key slots provided in the body portion at circumferentially spaced positions. 6. A furnace electrode clamp comprising, a metallic body portion of generally arcuate configuration and defining i. two key slots on one surface at circumferentially spaced positions, and ii. a water-coolant conduit running alongside the slots and providing go and return coolant paths a graphite p'ad mounted in, and retained by, each of said slots against which the electrode is to be clamped, the slots extending axially of the electrode whereby the pads may be inserted in, and removed from, the slots in a vertical sense.

7. A clamp according to claim 6, in which each key slot is a machined dovetail-like section having a planar inner wall matching the rear face of the pad, the front face of the pad being part-cylindrical to match the surface of the electrode.

8. A clamp according to claim 7, comprising,

a U-shaped band mounted for movement on the body perpendicular to the electrode axis and adapted to embrace the electrode to effect clamping thereof. 

1. A clamp for a non-consumable coated electrode in an electric arc furnace comprising: a metallic body portion defining a key slot on one surface thereon; a ''U'' shaped band mounted for movement on the body and adopted to embrace the electrode; and a graphite pad mounted in and retained by said slot against which the electrode is arranged to be clamped by said movable banD.
 2. A clamp according to claim 1, in which the key slot is a machined dovetail-like section extending axially of the electrode whereby the pad may be inserted in, and removed from, the slot in a vertical sense and in which a stop member is provided along the bottom of the slot against which the pad abuts.
 3. A clamp according to claim 2, in which the slot has a planar inner wall, matching the rear face of the pad, the front face of the pad being part-cylindrical to match the surface of the electrode.
 4. A clamp according to claim 3, in which the body defines a water-coolant conduit running alongside the pad.
 5. A clamp according to claim 4, comprising, at least two of said pads and a like number of key slots provided in the body portion at circumferentially spaced positions.
 6. A furnace electrode clamp comprising, a metallic body portion of generally arcuate configuration and defining i. two key slots on one surface at circumferentially spaced positions, and ii. a water-coolant conduit running alongside the slots and providing go and return coolant paths a graphite pad mounted in, and retained by, each of said slots against which the electrode is to be clamped, the slots extending axially of the electrode whereby the pads may be inserted in, and removed from, the slots in a vertical sense.
 7. A clamp according to claim 6, in which each key slot is a machined dovetail-like section having a planar inner wall matching the rear face of the pad, the front face of the pad being part-cylindrical to match the surface of the electrode.
 8. A clamp according to claim 7, comprising, a U-shaped band mounted for movement on the body perpendicular to the electrode axis and adapted to embrace the electrode to effect clamping thereof. 